Optical scanning systems for detecting bar codes provided on products are well known. Typically, these systems direct a light at the bar code which light is reflected to various degrees from the bar code whereby the spacing between individual light and dark bars of the code can be deciphered from the reflected light signal. Such reflecting systems operate well, but rely on a single signal from which the code is deciphered.
Eastman Kodak has recently introduced a new product into the market which includes edge code numbers in the form of bar codes provided at the edge of motion picture film. The film is manufactured in both negative and print film in 35 millimeters presently and will be introduced shortly into 16 millimeters product.
The edge code is exposed onto the film at the time of manufacturing by Eastman Kodak. The bar code pattern contains information relating to the manufacture and film type as well as a unique number. There is a unique bar code pattern every six inches of film stock. The unique number is such that it will not repeat on any position or roll of film for the next ten years of production. After the film is developed, the edge code becomes visible to the naked eye.
The edge code information gives an absolute indication of manufacture, film type, and location on the film in the number of feet and frames.
This edge code is provided at the edge beyond the perforations used to drive the film. The normal rate of travel of the film is approximately 1.5 feet per second, however, in fast forward or reverse, the speed of film travel can be about 15 feet per second. Thus, any scanning system must be capable of accurately reading the bar code, both at normal film speed as well as the higher rate of film speed used in a fast forward or reverse mode.
In contrast to bar codes placed on products, the exact characteristics of the film are not really known until the film has been developed. The properties of the bar code and the film can vary with the developing process as well as the overall speed of the film. The accuracy of the bar code is a result of the developing process and some loss in the exact edge distinction occurs due to the grain of the film as well as the effects of the development process which lowers the definition of the edges. The properties of one film to the next can vary considerably. With these factors, the bar code is difficult to consistently read.
When Kodak first introduced their edge code, they also introduced a reader circuit prototype which was capable of reading the bar code. Such a reader operated on the basis of a laser directed at the edge of the film producing light which was modulated by the bar code as the film moved past the light. The modulated light signal on the opposite side of the film was then used to decipher the bar code. With this type of structure, problems occurred with films of differing characteristics due to either their own characteristics and/or the effects of the development process. Such systems could be adjusted to operate, however the resulting structure was expensive and was not generally accepted in the marketplace.
There remains a need for a reader that can sense, decode and transmit or display the edge code accurately while still being relatively simple in operation and able to accommodate the varying characteristics of the film and the required speeds of recognition.